1. Field of the Invention
The common rail injection system serves to inject fuel into direct-injection internal combustion engines. In this common rail injection system, pressure generation and injection are decoupled from one another both in time and place. A separate high-pressure pump generates the injection pressure in a central high-pressure fuel reservoir. The onset of injection and the injection quantity are determined by the triggering time and triggering duration of injectors, actuated electrically, for instance, which communicate with the high-pressure fuel reservoir via fuel lines. In the common rail injection system, it is advantageous that the injection pressure is adapted to the load and rpm. The fuel injection is done at as high an injection pressure as possible. A high injection pressure has the advantages for instance of reduced pollutant emissions, reduced fuel consumption, and high specific outputs. The maximum injection pressures in common rail injection systems are limited to approximately 1800 bar by the high-pressure strength of pressure reservoirs (rails) and high-pressure pumps. For further increasing the injection pressure, a pressure booster can be employed in the injector. By means of a hydraulic boosting, the pressure booster converts a primary pressure, made available by the pressure reservoir, into the desired high injection pressure.
2. Prior Art
From German Patent Disclosure DE 4311627 A1, a fuel injection system is known in which the injection valves, to increase the injection pressure to up to 2000 bar, have a pressure booster. As a consequence of the reciprocating motion of a booster piston, the fuel pressure in an injection pressure chamber increases to a multiple of the high pressure applied. After the injection of fuel from the injection pressure chamber into a combustion chamber, the pressure in the injection pressure chamber drops as a result of the restoration of the booster piston. As a result, a check valve opens, so that fuel at the applied high pressure can flow into the injection pressure chamber (refilling). However, integrating such a check valve into a fuel injection system means considerable effort and expense in terms of production. It is difficult to accommodate the check valve in the installation space available.